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From:   Coiby Xu <coxu@redhat.com>
To:     kexec@lists.infradead.org
Cc:     Milan Broz <gmazyland@gmail.com>,
        Thomas Staudt <tstaudt@de.ibm.com>,
        Kairui Song <ryncsn@gmail.com>, dm-devel@redhat.com,
        Jan Pazdziora <jpazdziora@redhat.com>,
        Pingfan Liu <kernelfans@gmail.com>,
        Baoquan He <bhe@redhat.com>, Dave Young <dyoung@redhat.com>,
        linux-kernel@vger.kernel.org, Thomas Gleixner <tglx@linutronix.de>,
        Ingo Molnar <mingo@redhat.com>, Borislav Petkov <bp@alien8.de>,
        Dave Hansen <dave.hansen@linux.intel.com>,
        x86@kernel.org (maintainer:X86 ARCHITECTURE (32-BIT AND 64-BIT)),
        "H. Peter Anvin" <hpa@zytor.com>
Subject: [RFC v2 4/5] x86/crash: make the page that stores the LUKS volume key inaccessible
Date:   Fri,  4 Nov 2022 19:29:59 +0800
Message-Id: <20221104113000.487098-5-coxu@redhat.com>
In-Reply-To: <20221104113000.487098-1-coxu@redhat.com>
References: <20221104113000.487098-1-coxu@redhat.com>
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This adds an addition layer of protection for the saved copy of LUKS
volume key. Trying to access the saved copy will cause page fault.

Suggested-by: Pingfan Liu <kernelfans@gmail.com>
Signed-off-by: Coiby Xu <coxu@redhat.com>
---
 arch/x86/kernel/machine_kexec_64.c | 16 ++++++++++++++++
 1 file changed, 16 insertions(+)

diff --git a/arch/x86/kernel/machine_kexec_64.c b/arch/x86/kernel/machine_kexec_64.c
index 0611fd83858e..f3d51c38a1c9 100644
--- a/arch/x86/kernel/machine_kexec_64.c
+++ b/arch/x86/kernel/machine_kexec_64.c
@@ -557,9 +557,25 @@ static void kexec_mark_crashkres(bool protect)
 	kexec_mark_range(control, crashk_res.end, protect);
 }
 
+static void kexec_mark_luks_volume_key_inaccessible(void)
+{
+	unsigned long start, end;
+	struct page *page;
+	unsigned int nr_pages;
+
+	if (kexec_crash_image->luks_volume_key_addr) {
+		start = kexec_crash_image->luks_volume_key_addr;
+		end = start + kexec_crash_image->luks_volume_key_sz - 1;
+		page = pfn_to_page(start >> PAGE_SHIFT);
+		nr_pages = (end >> PAGE_SHIFT) - (start >> PAGE_SHIFT) + 1;
+		set_memory_np((unsigned long)page_address(page), nr_pages);
+	}
+}
+
 void arch_kexec_protect_crashkres(void)
 {
 	kexec_mark_crashkres(true);
+	kexec_mark_luks_volume_key_inaccessible();
 }
 
 void arch_kexec_unprotect_crashkres(void)
-- 
2.37.3